The present disclosure relates to a spool valve, and more particularly, to a spool valve that can individually control a flow rate and pressure of working fluid passing along a fluid path connecting a pump and a cylinder and a flow rate and pressure of working fluid passing along a fluid path connecting the cylinder and a tank.
A spool valve, i.e. a type of control valve, is commonly used in construction equipment, such as an excavator, and serves to supply working fluid, discharged by a hydraulic pump, to a hydraulic actuator.
In a spool valve of the related art, both a notch connecting pump and cylinder (P-C) paths and a notch connecting cylinder and tank (C-T) paths have been machined in a single spool. The notch connecting the pump-cylinder paths allows working fluid to be supplied to a cylinder by a pump, while the notch connecting the cylinder-tank paths allows working fluid to return to a tank from the cylinder. According to such a configuration, when the spool is moved by a change in the stroke of the spool, depending on pressure applied by a pilot signal, the same area of opening of the path, determined depending on the degree of alignment of the path and the notch, has accordingly been applied to both the pump-cylinder paths and the cylinder-tank paths. Thus, it has been actually impossible for the spool value of the related art to individually control the flow rates and pressures of working fluid passing along the pump-cylinder paths and the cylinder-tank paths in accordance with the operation of the cylinder acting as an actuator and load applied to the cylinder, thereby lowering fuel efficiency, which is problematic.
Accordingly, the present disclosure has been made while keeping the above-described problems occurring in the related art in consideration, and the present disclosure proposes a spool valve that can individually control a flow rate and pressure of working fluid passing along a fluid path connecting a pump and a cylinder and a flow rate and pressure of working fluid passing along a fluid path connecting the cylinder and a tank.
According to an aspect of the present disclosure, a spool valve may include: a valve block; a first spool disposed on one side within the valve block to be reciprocally movable in a longitudinal direction, and having a first notch provided in an outer circumferential surface thereof to be aligned with a first pump path and a first cylinder path, provided within the valve block, wherein the first spool controls a connection between the first pump path and the first cylinder path using the first notch when moving in response to a change in a stroke thereof; and a second spool disposed in the other side within the valve block to be reciprocally movable in a longitudinal direction, and having a second notch provided in an outer circumferential surface thereof to be aligned with a second cylinder path and a first tank path provided within the valve block, wherein the second spool controls a connection between the second cylinder path and the first tank path using the second notch when moving-in-response a change in a stroke thereof.
The spool valve may further include: a first spool cap coupled to the valve block, connected to the first spool, and providing a first port through which a pilot pressure is applied to change the stroke of the first spool; and a second spool cap coupled to the valve block, connected to tire second spool, and providing a second port through which a pilot pressure is applied to change the stroke of the second spool.
The spool valve may further include a third spool disposed within the valve block to face the second spool in a top-bottom direction and to be reciprocally movable in a longitudinal direction, and having a third notch provided in an outer circumferential surface thereof to be aligned with a second pump path and a third cylinder path provided within the valve block. The third spool controls a connection between the second pump path and the third cylinder path using the third notch when moving in response to a change in a stroke thereof.
The spool valve may further include a fourth spool disposed within the valve block to face the first spool in a top-bottom direction and to be reciprocally movable in a longitudinal direction, and having a fourth notch provided in an outer circumferential surface thereof to be aligned with a fourth cylinder path and a second tank path provided within the valve block. The fourth spool controls a connection between the fourth cylinder path and the second tank path using the fourth notch when moving in response to a change in a stroke thereof.
The spool valve may further include: a third spool cap coupled to the valve block, connected to the third spool, and providing a third port through which a pilot pressure is applied to change the stroke of the third spool; and a fourth spool cap coupled to the valve block, connected to the fourth spool, and providing a fourth port through which a pilot pressure is applied to change the stroke of the fourth spool.
The spool valve may further include a drain core provided between the first spool and the fourth spool and between the second spool and the third spoof.
The spool valve may further include a plurality of springs disposed within the first to fourth spool caps, respectively, to elastically support the first to fourth spools connected to the first to fourth spool caps.
The spool valve may further include a first actuator port provided in the valve block to connect the first cylinder path to a first cylinder line connected to a large chamber of the cylinder; and a second actuator port pro vided in the valve block to connect the second cylinder path to a second cylinder line connected to a small chamber of the cylinder.
The spool valve may further include a port relief valve disposed in the valve block to be connected to the first actuator port and the second actuator port.
The valve block may include: a pump core connecting the hydraulic pump to the first pump path to supply working fluid, discharged by the hydraulic pump, to the first pump path; and a tank core connecting the first, tank path to a tank to recover working fluid, returning from the cylinder along the first tank path, to the tank.
The valve block may further include a load check valve disposed between the first pump path and the pump core.
According to the present disclosure, since the spool controlling the connection between the pump path and the cylinder path and the spool controlling the connection between the cylinder path and the tank path are provided independently of each other, different levels of pilot pressure can be applied to the spools to move the spools, depending on the operations and loads of the cylinder acting as an actuator, thereby independently controlling the Sow rates and pressures of working fluid passing along the spools in a spool-specific manner.
In addition, according to the present disclosure, the areas of opening, i.e. the degrees of opening, of the spools controlling the connection between the pump path and the cylinder path and the connection between the cylinder path and the tank path can be adjusted, depending on the operations and loads of the cylinder, so that the operation of supplying working fluid to the cylinder by the pump and the operation of recovering working fluid to the tank from the cylinder can be efficiently controlled. This can consequently prevent excessive increases in the pressures of working fluid passing along the paths while efficiently regulating the flow rates of working fluid passing along the paths, thereby improving fuel efficiency and increasing the operating speed of the actuator.